DOS calculations for larger systems

[emilhfr]

Hi.

I am presently working with a rather large unit cell, such that the system capabilities of the computer i am running vasp on has become the bottleneck for the calculations.

I want to do a slightly denser k-point mesh for the DOS, but the memory requirements are prohibitive (20 irreducible k-points). Can i, in this case where i am using a constant electron density (ICHARG = 11), take the irreducible k-points and their weights as listed in the outcar for a certain mesh, split these into multiple calculations with explicit k-point lists, and add the resulting partial DOSCAR values together? Or is there a problem with this approach?`

Thank you.

[manuel_engel1]

Hi,

The method you propose is indeed possible but requires some work. Care must be taken that the individual calculations are compatible to each other (Fermi energy could be a concern). Keep in mind that the tetrahedron method (ISMEAR=-5) will not work in this case.

Alternatively, as of VASP 6.3.0, an optional k-point mesh can be supplied via the KPOINTS_OPT file. This can be used to perform DOS calculations on fine grids. In this case, VASP simultaneously operates only on a subset of these k-points, which substantially decreases the memory requirements. All this can be done in a single run. The results can then be read from the vasprun.xml (node <dos comment="kpoints_opt">) or, preferably, from the vaspout.h5 file if VASP was compiled with HDF5 support ("/results/electron_dos_kpoints_opt/").